Neurotransmitter

The rise of drug addiction has directed attention to the role of neurotransmitters by attempting to understand how it happens and how it can be counteracted. Cocaine and crack are psychostimulants that affect neurons containing dopamine in the limbic and frontal cortex of the brain; when they are used they generate a feelings of confidence and power. However, when large amounts are taken, people "crash" and suffer from physical and emotional exhaustion as well as depression. Opiates such as heroin and morphine appear to mimic naturally-occurring peptide substances in the brain with opiate activity called endorphins. Natural endorphins of the brain act to kill pain, cause sensations of pleasure, and cause sleepiness. Endorphins released with extensive aerobic exercise, for example, are responsible for the "rush" that long-distance runners experience.

It is believed that morphine and heroin combine with the endorphin receptors in the brain, resulting in reduced natural endorphin production. As a result, the drugs are needed to replace the naturally produced endorphins and addiction may occur. Attempts to counteract the effects involve using drugs that mimic them, such as nalorphine, naloxone, and naltrexone. One of the depressant drugs in widest use, alcohol, is believed to cause its effects by interacting with the GABA receptor. Initially anxiety is controlled, but greater amounts reduce muscle control and delay reaction time due to impaired thinking.